CHAP, iv.] ELECTRIC TELEGRAPHY. 581 



indicator, whose clockwork motion is provided with a key for winding 

 up, to the left at the back is the alarum. 



We have already said that the Morse system is adopted on a great 

 number of telegraphic lines in Europe, and is in general use through- 

 out America. By virtue of a generally adopted convention the 

 vocabulary of this system for letters, figures, stops, and special signals, 

 is that shown in Fig. 379. In Fig. 378 is reproduced the facsimile 

 of a message and its translation into the ordinary alphabet. 



An automatic form of Morse transmitter has recently been intro- 

 duced by Messrs. Siemens, which unites the two functions of 

 composing and transmitting messages automatically by means of a 

 single apparatus. The sending of a message is caused by pressing 

 down finger keys each of which corresponds to a letter, and the 

 message is received in the Morse character, the difference of the length 

 of these signs being independent of the time the finger keys are 



FIG. 378. Facsimile of a Morse message. 



pressed down. The transmitting speed of the instrument depends 

 upon the rapidity with which the finger keys are depressed; the 

 apparatus is capable of transmitting 90 messages an hour of 33 words 

 each. In construction the instrument consists of a cylinder wheel 

 the periphery of which is fitted with sliding pins placed close to each 

 other and parallel to the axis of the cylinder ; these pins when pushed 

 at one end by means of a lever attached to the finger key are deplaced 

 in the direction of the axis, and groups of deplaced pins in certain 

 combinations constitute the various types for the automatic transmission 

 of the signals, three deplaced pins in close succession represent a dash, 

 and a single deplaced pin between two in their normal position 1 a dot, 

 while one or more not de aced signify an interval of more or less 

 length. 



Thus upon pressing down a finger key a group of pins is deplaced 



